The present invention relates to a combination timepiece and calculator and more particularly to an electronic timepiece having an arithmetic calculation capability.
In general a combination timepiece and calculator includes a power source, a time keeping circuit, a calculation circuit, a keyboard unit for introducing information into the calculation circuit, a display unit for displaying information stored in the time keeping circuit and the calculation circuit, and a mode switch for controlling the power supply to the calculation circuit.
A typical construction of a combination wristwatch and calculator is shown in, for example, U.S. Pat. No. 3,928,960, Robert O. Reese "COMBINATION WRISTWATCH AND CALCULATOR," issued on Dec. 30, 1975.
Generally, an electronic digital timepiece consumes little power and, more particularly, consumes power of below twenty microwatts (20 .mu.W). Therefore, the electronic digital timepiece can continuously work for more than one (1) year without changing its power source such as a cell, or charging up its battery. Whereas, an electronic calculator consumes considerably large power and, more specifically, of about ten milliwatts (10 mW). It will be clear that the electronic calculator consumes power of from one hundred (100) to one thousand (1,000) times that of an electronic digital timepiece. Accordingly, in a combination timepiece and calculator, the total power dissipation of the power source is mostly determined by the time period when the electronic calculator is actually operated. Therefore, there is a possibility that the electronic digital timepiece, though it is not preferable, ceases its operation after considerably short period operation. Needless to say, sudden termination of the timepiece operation causes trouble and, therefore, the cell must be exchanged or the battery must be charged up before the electronic timepiece ceases its operation.